Researchers at Sandia, a National Nuclear Security Administration (NNSA) laboratory in Bushland, Texas, and Knight & Carver (K&C) of San Diego are in the process of testing a new wind turbine blade the companies have developed.

Named STAR (for Sweep Twist Adaptive Rotor), the blade is the first of its kind produced at a utility-grade size. The blades have a gently curved tip, termed "sweep," which is designed for low-wind-speed regions. They are 27.1 meters long - almost three meters longer than the baseline they will replace.

"This design allows the blade to twist more than traditional designs, thus relieving some of the effects of gusty turbulent wind on blade life," says Tom Ashwill, who leads Sandia's blade research efforts. "This then allows us to grow the blade length for the same rotor, providing for increased energy capture of five to 10 percent and yet retaining the same expected fatigue life."

The sites targeted by this effort have annual average wind speeds of 5.8 meters per second, measured at a 10-meter height. Such sites are abundant in the U.S. and would increase by 20-fold the available land area that can be developed for wind energy, the companies say.

The K&C contract is part of the Low Wind Speed Technology (LWST) project that targets wind sites that are not the strongest but plentiful. In late 2005, the Department of Energy and Sandia awarded K&C the $2 million contract for the research, which includes $800,000 in K&C cost share. Because of budget reallocations, this project was the only one of several LWST projects to receive 2007 funding.

According to the companies, the first STAR blade was tested in January at K&C's fabrication facility in San Diego to determine its bending and twist behavior due to static loads. In addition, natural frequencies were measured. These data will be compared to design simulations to determine how well the design concept performs. Four additional blades - three of which will be flight-tested on a turbine in Iowa - will be fabricated in the first quarter of 2007, the companies add.

Other members of the design team are Dynamic Design of Davis, Calif.; MDZ Consulting of Clear Lake Shores, Texas; University of California, Davis; and NSE Composites of Seattle. Sandia's role in the project has been directing design and test planning. The K&C team provided the design and blade fabrication.